An opera singer from the USA seemed just like the rest when she stepped onto the BGT stage, but it was clear she wasn't as she seemed once Ant McPartlin and Dec Donnelly were forced to involve themselves in her performance.

Sarah Llewellyn, a 32-year-old from America, said she would be performing opera for the panel, and the sounds of O Mio Babino Caro blared through the speakers.

The audience were into it and Simon Cowell couldn't believe the amazing voice she had - and then things got weird.

(Image: REX/Shutterstock)

Suddenly, Ant and Dec rolled onto stage with a large, white wedding cake, and Sarah pulled a fork from her cleavage.

She started frantically poking at the cake, trying to get a large mouthful, then started messily eating it as she sang.

Sarah continued and Ant and Dec could not believe the ferocity with which she ate her cake, until suddenly she flicks a clasp and her entire dress falls to the floor.

Her version of O Mio Babino Caro was stunning... (Image: PA)

A red-faced Ant looked away as Dec's jaw dropped, and it seemed the crowd were equally bemused by the act.

She then beckoned Ant over, who took hold of her microphone as she lowered herself downwards into a bridge-shape, showing off her apparent skills as a contortionist.

Needless to say, Simon was stunned as Amanda Holden shoved his shoulder in laughter.

...until she shoved cake in her mouth (Image: REX/Shutterstock)

In the end, Ant was lying on the floor trying to keep her mic close to her mouth, while Dec stared on in amazement holding the top tier of the cake.

Sarah did some saucy moves at this point, which earned her some wolf whistles from the crowd, and David Walliams and Alesha Dixon could not contain their laughter as she took her final position.

She flipped back into her bridge, handing the mic back to Ant to make sure it was in the right place, as she lowered her whole face into the cake while finishing off her beautiful aria.

She then ripped off her evening gown (Image: REX/Shutterstock)

As she finished the crowd cheered and Ant stood up with his arms out, cheering her on for the mad performance.

As the duo left the stage, Dec said: "I thought we were just taking on a bit of cake?"

Ant replied: "I did not expect that to happen!" as he licked icing off his finger.

The two were in fits of giggles as Amanda, back in the arena, exclaimed that Sarah's act could be the perfect thing for Prince Harry and Meghan Markle's wedding.

Moments later she was sprawled on the floor (Image: REX/Shutterstock)

She said: "This is perfect for the royal family. you could be the entertainment and Meghan and Harry's wedding, you could eat their wedding cake, and sing!"

David added: "You've have combined all the things you're good at - singing opera being bendy and eating cake."

Fans loved how Ant was required to follow Sarah around with a mic, despite being a little confused that she was given four yeses from the judges for her originality.